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	<head>
		<title>three.js webgl - percent closer soft-shadows</title>
		<meta charset="utf-8">
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		<style>
			body {
				background-color: #cce0ff;
				color: #000;
			}
			a {
				color: #08f;
			}
		</style>
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	<body>
		<div id="info">Percent Closer Soft-Shadows (PCSS) by <a href="http://eduperiment.com">spidersharma03</a></div>

		<script type="x-shader/x-fragment" id="PCSS">

				#define LIGHT_WORLD_SIZE 0.005
				#define LIGHT_FRUSTUM_WIDTH 3.75
				#define LIGHT_SIZE_UV (LIGHT_WORLD_SIZE / LIGHT_FRUSTUM_WIDTH)
				#define NEAR_PLANE 9.5

				#define NUM_SAMPLES 17
				#define NUM_RINGS 11
				#define BLOCKER_SEARCH_NUM_SAMPLES NUM_SAMPLES

				vec2 poissonDisk[NUM_SAMPLES];

				void initPoissonSamples( const in vec2 randomSeed ) {
					float ANGLE_STEP = PI2 * float( NUM_RINGS ) / float( NUM_SAMPLES );
					float INV_NUM_SAMPLES = 1.0 / float( NUM_SAMPLES );

					// jsfiddle that shows sample pattern: https://jsfiddle.net/a16ff1p7/
					float angle = rand( randomSeed ) * PI2;
					float radius = INV_NUM_SAMPLES;
					float radiusStep = radius;

					for( int i = 0; i < NUM_SAMPLES; i ++ ) {
						poissonDisk[i] = vec2( cos( angle ), sin( angle ) ) * pow( radius, 0.75 );
						radius += radiusStep;
						angle += ANGLE_STEP;
					}
				}

				float penumbraSize( const in float zReceiver, const in float zBlocker ) { // Parallel plane estimation
					return (zReceiver - zBlocker) / zBlocker;
				}

				float findBlocker( sampler2D shadowMap, const in vec2 uv, const in float zReceiver ) {
					// This uses similar triangles to compute what
					// area of the shadow map we should search
					float searchRadius = LIGHT_SIZE_UV * ( zReceiver - NEAR_PLANE ) / zReceiver;
					float blockerDepthSum = 0.0;
					int numBlockers = 0;

					for( int i = 0; i < BLOCKER_SEARCH_NUM_SAMPLES; i++ ) {
						float shadowMapDepth = unpackRGBAToDepth(texture2D(shadowMap, uv + poissonDisk[i] * searchRadius));
						if ( shadowMapDepth < zReceiver ) {
							blockerDepthSum += shadowMapDepth;
							numBlockers ++;
						}
					}

					if( numBlockers == 0 ) return -1.0;

					return blockerDepthSum / float( numBlockers );
				}

				float PCF_Filter(sampler2D shadowMap, vec2 uv, float zReceiver, float filterRadius ) {
					float sum = 0.0;
					float depth;
					#pragma unroll_loop_start
					for( int i = 0; i < 17; i ++ ) {
						depth = unpackRGBAToDepth( texture2D( shadowMap, uv + poissonDisk[ i ] * filterRadius ) );
						if( zReceiver <= depth ) sum += 1.0;
					}
					#pragma unroll_loop_end
					#pragma unroll_loop_start
					for( int i = 0; i < 17; i ++ ) {
						depth = unpackRGBAToDepth( texture2D( shadowMap, uv + -poissonDisk[ i ].yx * filterRadius ) );
						if( zReceiver <= depth ) sum += 1.0;
					}
					#pragma unroll_loop_end
					return sum / ( 2.0 * float( 17 ) );
				}

				float PCSS ( sampler2D shadowMap, vec4 coords ) {
					vec2 uv = coords.xy;
					float zReceiver = coords.z; // Assumed to be eye-space z in this code

					initPoissonSamples( uv );
					// STEP 1: blocker search
					float avgBlockerDepth = findBlocker( shadowMap, uv, zReceiver );

					//There are no occluders so early out (this saves filtering)
					if( avgBlockerDepth == -1.0 ) return 1.0;

					// STEP 2: penumbra size
					float penumbraRatio = penumbraSize( zReceiver, avgBlockerDepth );
					float filterRadius = penumbraRatio * LIGHT_SIZE_UV * NEAR_PLANE / zReceiver;

					// STEP 3: filtering
					//return avgBlockerDepth;
					return PCF_Filter( shadowMap, uv, zReceiver, filterRadius );
				}

		</script>

		<script type="x-shader/x-fragment" id="PCSSGetShadow">

			return PCSS( shadowMap, shadowCoord );

		</script>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import Stats from 'three/addons/libs/stats.module.js';

			import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

			let stats;
			let camera, scene, renderer;

			let group;

			init();

			function init() {

				const container = document.createElement( 'div' );
				document.body.appendChild( container );

				// scene

				scene = new THREE.Scene();
				scene.fog = new THREE.Fog( 0xcce0ff, 5, 100 );

				// camera

				camera = new THREE.PerspectiveCamera( 30, window.innerWidth / window.innerHeight, 1, 10000 );

				// We use this particular camera position in order to expose a bug that can sometimes happen presumably
				// due to lack of precision when interpolating values over really large triangles.
				// It reproduced on at least NVIDIA GTX 1080 and GTX 1050 Ti GPUs when the ground plane was not
				// subdivided into segments.
				camera.position.x = 7;
				camera.position.y = 13;
				camera.position.z = 7;

				scene.add( camera );

				// lights

				scene.add( new THREE.AmbientLight( 0xaaaaaa, 3 ) );

				const light = new THREE.DirectionalLight( 0xf0f6ff, 4.5 );
				light.position.set( 2, 8, 4 );

				light.castShadow = true;
				light.shadow.mapSize.width = 1024;
				light.shadow.mapSize.height = 1024;
				light.shadow.camera.far = 20;

				scene.add( light );

				// scene.add( new DirectionalLightHelper( light ) );
				scene.add( new THREE.CameraHelper( light.shadow.camera ) );

				// group

				group = new THREE.Group();
				scene.add( group );

				const geometry = new THREE.SphereGeometry( 0.3, 20, 20 );

				for ( let i = 0; i < 20; i ++ ) {

					const material = new THREE.MeshPhongMaterial( { color: Math.random() * 0xffffff } );

					const sphere = new THREE.Mesh( geometry, material );
					sphere.position.x = Math.random() - 0.5;
					sphere.position.z = Math.random() - 0.5;
					sphere.position.normalize();
					sphere.position.multiplyScalar( Math.random() * 2 + 1 );
					sphere.castShadow = true;
					sphere.receiveShadow = true;
					sphere.userData.phase = Math.random() * Math.PI;
					group.add( sphere );

				}

				// ground

				const groundMaterial = new THREE.MeshPhongMaterial( { color: 0x898989 } );

				const ground = new THREE.Mesh( new THREE.PlaneGeometry( 20000, 20000, 8, 8 ), groundMaterial );
				ground.rotation.x = - Math.PI / 2;
				ground.receiveShadow = true;
				scene.add( ground );

				// column

				const column = new THREE.Mesh( new THREE.BoxGeometry( 1, 4, 1 ), groundMaterial );
				column.position.y = 2;
				column.castShadow = true;
				column.receiveShadow = true;
				scene.add( column );

				// overwrite shadowmap code

				let shader = THREE.ShaderChunk.shadowmap_pars_fragment;

				shader = shader.replace(
					'#ifdef USE_SHADOWMAP',
					'#ifdef USE_SHADOWMAP' +
					document.getElementById( 'PCSS' ).textContent
				);

				shader = shader.replace(
					'#if defined( SHADOWMAP_TYPE_PCF )',
					document.getElementById( 'PCSSGetShadow' ).textContent +
					'#if defined( SHADOWMAP_TYPE_PCF )'
				);

				THREE.ShaderChunk.shadowmap_pars_fragment = shader;

				// renderer

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.setAnimationLoop( animate );
				renderer.setClearColor( scene.fog.color );

				container.appendChild( renderer.domElement );

				renderer.shadowMap.enabled = true;

				// controls
				const controls = new OrbitControls( camera, renderer.domElement );
				controls.maxPolarAngle = Math.PI * 0.5;
				controls.minDistance = 10;
				controls.maxDistance = 75;
				controls.target.set( 0, 2.5, 0 );
				controls.update();

				// performance monitor

				stats = new Stats();
				container.appendChild( stats.dom );

				//

				window.addEventListener( 'resize', onWindowResize );

			}

			//

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			//

			function animate() {

				const time = performance.now() / 1000;

				group.traverse( function ( child ) {

					if ( 'phase' in child.userData ) {

						child.position.y = Math.abs( Math.sin( time + child.userData.phase ) ) * 4 + 0.3;

					}

				} );

				renderer.render( scene, camera );

				stats.update();

			}

		</script>
	</body>
</html>
